Although high humidity can occasionally cause condensation, ultimately, low humidity is the greatest threat to an acoustic guitar. In winter months when furnaces are on, humidity in the average home drops to about 20%. This extreme dryness can cause the thin woods in an acoustic guitar to shrink and crack, and will not be covered by any guitar company’s warrantee. An acoustic guitar is best kept stable at humidity levels of 45% or above. In the shop we keep the relative humidity between 45 and 60%. We do this through the use of a central humidification unit, and monitor the levels with two digital and one analog hygrometers, located throughout the store. Some of you have this, or other types of home humidifiers, but for the rest of you I recommend using inexpensive passive humidifiers like those pictured above. This type of humidifier consists of a sponge inside of a vinyl or surgical rubber casing, with holes that allow the water to evaporate at a controlled rate. To use it, simply soak the humidifier in tap water, ring out the excess, and wipe off the casing, (to prevent water from dripping inside of your guitar).Then insert it into the soundhole of the acoustic guitar. Repeat this every 3-4 days, or more frequently during really cold Winter days. Some guitar cases now come with built in humidity guages, and we sell affordable analog and digital versions (pictured above) which can also track recent low and high temperature and humidity readings. If you need help please contact us. (Wade's Home Page)